Electronic device and method for controlling electronic device

ABSTRACT

An echo caused by sound leakage from a housing that vibrates due to a vibrating body is reduced. An electronic device ( 1 ) according to the present invention includes a piezoelectric element ( 30 ), a vibrating plate ( 10 ) that vibrates due to the piezoelectric element ( 30 ), microphones ( 42, 43 ), and an equalizer ( 44 ), the electronic device ( 1 ) causing the vibrating plate ( 10 ) to generate air-conducted sound and vibration sound that is transmitted by vibrating a part of a human body. The equalizer ( 44 ) makes a low-range emphasis setting, to emphasize a low frequency range more than a high frequency range of the air-conducted sound, when the volume of the air-conducted sound collected by the microphones ( 42, 43 ) exceeds a predetermined threshold.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japanese PatentApplication No. 2012-116758 filed May 22, 2012, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electronic device and a method forcontrolling an electronic device that vibrate a panel by applying apredetermined electric signal (audio signal) to a piezoelectric elementand that transmit air-conducted sound and vibration sound to a user bytransmitting the vibration of the panel to the user's body.

BACKGROUND

Patent Literature 1 recites an electronic device, such as a mobile phoneor the like, that transmits air-conducted sound and bone-conducted soundto a user. As the air-conducted sound, Patent Literature 1 recites asound that is transmitted to the user's auditory nerve by airvibrations, caused by a vibrating object, that are transmitted throughthe external ear canal to the eardrum and cause the eardrum to vibrate.As bone-conducted sound, Patent Literature 1 recites a sound that istransmitted to the user's auditory nerve through a portion of the user'sbody (such as the cartilage of the outer ear) that is contacting avibrating object.

Patent Literature 1 recites a telephone in which a rectangular vibratingbody, formed from a piezoelectric bimorph and a flexible substance, isattached to an outer surface of a housing via an elastic member. PatentLiterature 1 also discloses that when voltage is applied to thepiezoelectric bimorph in the vibrating body, the piezoelectric materialexpands and contracts in the longitudinal direction, causing thevibrating body to undergo flexure vibration. Air-conducted sound andbone-conducted sound are transmitted to the user when the user contactsthe vibrating body to the auricle.

CITATION LIST

Patent Literature 1: JP 2005-348193 A

SUMMARY

In the electronic device disclosed in Patent Literature 1, the housingof the telephone vibrates due to the vibrating body. In order for theuser to appropriately hear air-conducted sound and bone-conducted sound,the user needs to press the ear to a predetermined position of thehousing. When the position pressed by the user's ear is misaligned, theair-conducted sound may leak and be transmitted to a sound collectingmicrophone, generating an echo. Patent Literature 1, however, does nottake into consideration measures against such an echo.

The present invention provides an electronic device and a method forcontrolling an electronic device that can reduce an echo caused by soundleakage from the housing that vibrates due to a vibrating body.

An electronic device according to the present invention includes: apiezoelectric element; a vibrating plate configured to vibrate due tothe piezoelectric element; a microphone; and an equalizer, theelectronic device causing the vibrating plate to generate air-conductedsound and vibration sound that is transmitted by vibrating a part of ahuman body, and the equalizer making a low-range emphasis setting, toemphasize a low frequency range more than a high frequency range of theair-conducted sound, when a volume of the air-conducted sound collectedby the microphone exceeds a predetermined threshold.

The microphone may be a first microphone that collects speech of a user,and the equalizer may make the low-range emphasis setting when a volumeof the air-conducted sound collected by the first microphone exceeds afirst threshold.

The vibrating plate may be positioned in an expected contact region of ahousing where an ear of a user is expected to contact, and the firstmicrophone may be provided in a mouth-neighboring region of the housingnear a mouth of the user.

The microphone may be a second microphone that collects surroundingsound, and the equalizer may make the low-range emphasis setting when avolume of the air-conducted sound collected by the second microphoneexceeds a second threshold.

The vibrating plate may be positioned in an expected contact region of ahousing where an ear of a user is expected to contact, and the secondmicrophone may be provided on an opposite face from the vibrating plateof the housing.

The electronic device may further include, as the microphone, a firstmicrophone that collects speech of a user and a second microphone thatcollects surrounding sound, and the equalizer may make the low-rangeemphasis setting when a volume of the air-conducted sound collected bythe first microphone exceeds a first threshold or when a volume of theair-conducted sound collected by the second microphone exceeds a secondthreshold.

A method according to the present invention for controlling anelectronic device that includes a piezoelectric element, a vibratingplate configured to vibrate due to the piezoelectric element, amicrophone, and an equalizer, the electronic device causing thevibrating plate to generate air-conducted sound and vibration sound thatis transmitted by vibrating a part of a human body includes the step of:making a low-range emphasis setting, for the equalizer to emphasize alow frequency range more than a high frequency range of theair-conducted sound, when a volume of the air-conducted sound collectedby the microphone exceeds a predetermined threshold.

The microphone may be a first microphone that collects speech of a user,and the equalizer may make the low-range emphasis setting when a volumeof the air-conducted sound collected by the first microphone exceeds afirst threshold.

The microphone may be a second microphone that collects surroundingsound, and the equalizer may make the low-range emphasis setting when avolume of the air-conducted sound collected by the second microphoneexceeds a second threshold.

The electronic device may further include, as the microphone, a firstmicrophone that collects speech of a user and a second microphone thatcollects surrounding sound, and the equalizer may make the low-rangeemphasis setting when a volume of the air-conducted sound collected bythe first microphone exceeds a first threshold or when a volume of theair-conducted sound collected by the second microphone exceeds a secondthreshold.

An electronic device according to the present invention includes: apiezoelectric element; a vibrating plate configured to vibrate due tothe piezoelectric element; a main microphone; a sub-microphone; and acontrol unit, the electronic device causing the vibrating plate togenerate air-conducted sound and vibration sound that is transmitted byvibrating a part of a human body, and the control unit controlling thepiezoelectric element so as to suppress or reduce vibration of thevibrating plate when a difference between a volume of the air-conductedsound collected by the first microphone and a volume of theair-conducted sound collected by the second microphone exceeds apredetermined threshold.

A method according to the present invention for controlling anelectronic device that includes a piezoelectric element, a vibratingplate configured to vibrate due to the piezoelectric element, a mainmicrophone, a sub-microphone, and a control unit, the electronic devicecausing the vibrating plate to generate air-conducted sound andvibration sound that is transmitted by vibrating a part of a human bodyincludes the step of: controlling, via the control unit, thepiezoelectric element so as to suppress or reduce vibration of thevibrating plate when a difference between a volume of the air-conductedsound collected by the first microphone and a volume of theair-conducted sound collected by the second microphone exceeds apredetermined threshold.

According to the electronic device and the method for controlling anelectronic device of the present invention, it is possible to reduce anecho caused by sound leakage from the housing that vibrates due to avibrating body.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be further described below with reference tothe accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an electronic device accordingto an embodiment of the present invention;

FIG. 2 illustrates an appropriate configuration of a panel;

FIGS. 3(a) and 3(b) illustrate an overview of echo generation due to theposition pressed by the ear;

FIG. 4 illustrates an example of sound leakage characteristics of apiezoelectric receiver;

FIG. 5 is a flowchart of low-range emphasis setting based on soundcollection by the main microphone;

FIG. 6 is a flowchart of low-range emphasis setting based on soundcollection by the sub-microphone;

FIG. 7 is a flowchart of low-range emphasis setting based on soundcollection by the main microphone and the sub-microphone;

FIG. 8 is a flowchart of receiver volume level setting;

FIGS. 9(a) and 9(b) illustrate a housing structure of the electronicdevice according to Embodiment 1;

FIG. 10 illustrates an example of vibration of a panel in the electronicdevice according to Embodiment 1;

FIGS. 11(a), 11(b), and 11(c) illustrate a housing structure of theelectronic device according to Embodiment 2;

FIG. 12 illustrates an example of vibration of a panel in the electronicdevice according to Embodiment 2; and

FIG. 13 illustrates an example of joining the panel and the housing.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail withreference to the accompanying drawings. FIG. 1 is a functional blockdiagram of an electronic device 1 according to an embodiment of thepresent invention. The electronic device 1 is, for example, a mobilephone (smartphone) and is provided with a panel 10, a display unit 20, apiezoelectric element 30, an input unit 40, and a control unit 50.Furthermore, the electronic device 1 is provided with a transceiver 41,a main microphone 42 (first microphone), a sub-microphone 43 (secondmicrophone), and an equalizer 44. The transceiver 41 has a well-knownstructure and is connected wirelessly to a communications networkthrough a base station or the like. The main microphone 42 and thesub-microphone 43 are well-known microphones, such as a condensermicrophone or the like, and collect sound such as speech by the user,surrounding sound, and the like during a conversation through thetransceiver 41. The main microphone 42 mainly collects speech by theuser and is provided in a mouth-neighboring region of the housing nearthe mouth of the user. The sub-microphone 43 mainly collects surroundingsound and is provided on the opposite face from the panel 10 in thehousing of the electronic device 1. The equalizer 44 adjusts thefrequency characteristics of the air-conducted sound generated byvibration, and in greater detail, adjusts the electric signal applied tothe piezoelectric element 30 by the control unit 50.

The panel 10 is a touch panel that detects contact, a cover panel thatprotects the display unit 20, or the like. The panel 10 functions as avibrating plate that vibrates due to the piezoelectric element 30. Thepanel 10 is positioned in an expected contact region of the housingwhere the user's ear is expected to contact. For example, the expectedcontact region is the front face of the housing contacted by the user'sear. The panel 10 is, for example, made from glass or a synthetic resinsuch as acrylic or the like. The panel 10 is preferably plate-like inshape. The panel 10 may be a flat plate or may be a curved panel, thesurface of which is smoothly inclined. When the panel 10 is a touchpanel, the panel 10 detects contact by the user's finger, a pen, astylus pen, or the like. Any detection system may be used in the touchpanel, such as a capacitive system, a resistive film system, a surfaceacoustic wave system (or an ultrasonic wave system), an infrared system,an electromagnetic induction system, a load detection system, or thelike.

The display unit 20 is a display device such as a liquid crystaldisplay, an organic EL display, an inorganic EL display, or the like.The display unit 20 is provided on the back face of the panel 10. Thedisplay unit 20 is disposed on the back face of the panel 10 by ajoining member (for example, adhesive). The display unit 20 may beadhered to the panel 10 by a joining member (for example, adhesive) ordisposed at a distance from the panel 10 and supported by the housing ofthe electronic device 1.

The piezoelectric element 30 is formed by elements that, uponapplication of an electric signal (voltage), either expand and contractor flex (bend) in accordance with the electromechanical couplingcoefficient of their constituent material. Ceramic or crystal elements,for example, are used. The piezoelectric element 30 may be a unimorph,bimorph, or laminated piezoelectric element. Examples of a laminatedpiezoelectric element include a laminated unimorph element with layersof unimorph (for example, 16 or 24 layers) and a laminated bimorphelement with layers of bimorph (for example, 16 or 24 layers). Such alaminated piezoelectric element may be configured with a laminatedstructure formed by a plurality of dielectric layers composed of, forexample, lead zirconate titanate (PZT) and electrode layers disposedbetween the dielectric layers. Unimorph expands and contracts upon theapplication of an electric signal (voltage), and bimorph flexes upon theapplication of an electric signal (voltage).

The piezoelectric element 30 is disposed on the back face of the panel10 (the face on the inner side of the electronic device 1). Thepiezoelectric element 30 is attached to the panel 10 by a joining member(for example, double-sided tape). The piezoelectric element 30 may beattached to the panel 10 with an intermediate member (for example, sheetmetal) therebetween. Once disposed on the back face of the panel 10, thepiezoelectric element 30 is separated from the inner surface of ahousing 60 by a predetermined distance. The piezoelectric element 30 ispreferably separated from the inner surface of the housing 60 by thepredetermined distance even when expanding and contracting or flexing.In other words, the distance between the piezoelectric element 30 andthe inner face of the housing 60 is preferably larger than the maximumamount of deformation of the piezoelectric element 30.

The input unit 40 accepts operation input from the user and may beconfigured, for example, using operation buttons (operation keys). Notethat when the panel 10 is a touch panel, the panel 10 can also acceptoperation input from the user by detecting contact by the user.

The control unit 50 is a processor that controls the electronic device1. The control unit 50 applies a predetermined electric signal (avoltage corresponding to an audio signal) to the piezoelectric element30 via the equalizer 44. The voltage that the control unit 50 applies tothe piezoelectric element 30 may, for example, be ±15 V. This is higherthan ±5 V, i.e. the applied voltage of a so-called panel speaker forconduction of sound by air-conducted sound rather than vibration sound.In this way, even if the user presses the panel 10 against the user'sbody for example with a force of 3 N or greater (a force of 5 N to 10N), sufficient vibration is generated in the panel 10, so that avibration sound can be generated via a part of the user's body. Notethat the magnitude of the applied voltage used may be appropriatelyadjusted in accordance with the fixation strength of the panel 10 withrespect to the housing or a support member, or in accordance with theperformance of the piezoelectric element 30. Upon the control unit 50applying the electric signal to the piezoelectric element 30, thepiezoelectric element 30 expands and contracts or flexes in thelongitudinal direction. At this point, the panel 10 to which thepiezoelectric element 30 is attached deforms in conjunction with theexpansion and contraction or flexing of the piezoelectric element 30.The panel 10 thus vibrates. The panel 10 flexes due to expansion andcontraction or to bending of the piezoelectric element 30. The panel 10is bent directly by the piezoelectric element 30. Stating that “thepanel 10 is bent directly by the piezoelectric element” differs from thephenomenon utilized in known panel speakers, whereby the panel deformsupon vibration of a particular region of the panel due to the inertialforce of a piezoelectric actuator constituted by a piezoelectric elementdisposed in the casing. Stating that “the panel 10 is bent directly bythe piezoelectric element” refers instead to how expansion andcontraction or bending (flexure) of the piezoelectric element directlybends the panel via the joining member or via the joining member and thebelow-described reinforcing member 80. Therefore, along with generatingair-conducted sound, the panel 10 generates vibration sound via a partof the user's body when the user brings a part of the body (such as thecartilage of the outer ear) into contact. For example, the control unit50 can apply an electric signal, corresponding to an audio signalrelated to the other party's voice, to the piezoelectric element 30 togenerate air-conducted sound and vibration sound that correspond to theaudio signal. The audio signal may be related to ringtones, musicincluding songs, or the like. Note that the audio signal pertaining tothe electric signal may be based on music data stored in internal memoryof the electronic device 1, or may be music data stored on an externalserver or the like and played back over a network.

The panel 10 vibrates not only in the region in which the piezoelectricelement 30 is attached, but also in a region separate from theattachment region. In the region of vibration, the panel 10 includes aplurality of locations at which the panel 10 vibrates in a directionintersecting the main surface of the panel 10. At each of theselocations, the value of the vibration amplitude changes over time frompositive to negative or vice-versa. At a given instant during vibrationof the panel 10, portions with a relatively large vibration amplitudeand portions with a relatively small vibration amplitude appear to bedistributed randomly or cyclically over nearly the entire panel 10. Inother words, a plurality of vibration waves are detected across theentire panel 10. The voltage that the control unit 50 applies to thepiezoelectric element 30 may be ±15 V to prevent dampening of theabove-described vibration of the panel 10 even if the user presses thepanel 10 against the user's body with a force of, for example, 5 N to 10N. Therefore, the user can hear sound by contacting a region distantfrom the above-described attachment region of the panel 10 to the ear.

The panel 10 may be nearly the same size as the user's ear. Asillustrated in FIG. 2, the panel 10 may also be larger than the user'sear. Adopting such a size makes it easier for the panel 10 of theelectronic device 1 to cover the entire ear when the user listens tosound, thus making it difficult for surrounding sounds (noise) to enterthe external ear canal. The region of the panel 10 that vibrates shouldbe larger than a region having a length corresponding to the distancefrom the inferior antihelix crus to the antitragus and a widthcorresponding to the distance from the tragus to the antihelix. Theregion of the panel 10 that vibrates preferably has a lengthcorresponding to the distance from a position in the helix near thesuperior antihelix crus to the earlobe and a width corresponding to thedistance from the tragus to a position in the helix near the antihelix.The region with the above length and width may be a rectangular regionor may be an elliptical region with the above length as the major axisand the above width as the minor axis. The average size of a Japaneseperson's ear can be looked up in sources such as the Japanese BodyDimension Data (1992-1994) gathered by the Research Institute of HumanEngineering for Quality Life (HQL). Note that if the panel 10 is atleast as large as the average size of a Japanese person's ear, it isthought that the panel 10 will be a size capable of covering the entireear of most non-Japanese people.

By vibration of the panel 10, the electronic device 1 can transmitvibration sound through a part of the user's body (such as the cartilageof the outer ear) and air-conducted sound to the user. Therefore, whensound is output at a volume equivalent to a known dynamic receiver, thesound that is transmitted to the periphery of the electronic device 1 byair vibrations due to vibration of the panel 10 is smaller than with adynamic receiver. Accordingly, the electronic device 1 is appropriatefor listening to recorded messages, for example, on the train or thelike.

The electronic device 1 generates a sound transmitted inside the humanbody by vibration of the panel 10 caused by the piezoelectric element30. The sound transmitted inside the human body vibrates the middle earor the inner ear via soft tissue (such as cartilage) of the human body.The electronic device 1 transmits vibration sound by vibration of thepanel 10, and therefore even if the user is wearing earphones orheadphones, for example, the user can hear sound through the earphonesor headphones and through a part of the body by contacting theelectronic device 1 against the earphones or headphones.

The electronic device 1 transmits sound to a user by vibration of thepanel 10. Therefore, if the electronic device 1 is not provided with aseparate dynamic receiver, it is unnecessary to form an opening (sounddischarge port) for sound transmission in the housing, therebysimplifying waterproof construction of the electronic device 1. On theother hand, if the electronic device 1 is provided with a dynamicreceiver, the sound discharge port should be blocked by a memberpermeable by air but not liquid. Gore-Tex (registered trademark) is anexample of a member permeable by air but not liquid.

Furthermore, the electronic device 1 reduces an echo caused by soundleakage generated when the position on the housing pressed by the user'sear is misaligned. In order to appropriately hear air-conducted soundand vibration sound generated by vibration, the user needs to press theear to a predetermined position of the housing. When the position on thehousing pressed by the user's ear is misaligned, the air-conducted soundmay leak and be transmitted to a sound collecting microphone, generatingan echo. FIGS. 3(a) and 3(b) illustrate an overview of echo generationdue to the position pressed by the ear. FIG. 3(a) is an example of anappropriate position pressed by the ear, whereas FIG. 3(b) illustratesan example of the position pressed by the ear being misaligned.Comparing the appropriate position pressed by the ear and the misalignedposition pressed by the ear shows that for the misaligned positionpressed by the ear, air-conducted sound due to vibration easily leaks tothe surrounding area, and an echo is generated by receiver audio beingtransmitted to the main microphone and the sub-microphone.

In the piezoelectric receiver that vibrates the panel 10 with thepiezoelectric element 30, the amount of sound leakage in the highfrequency component is higher than for a typical dynamic receiver. FIG.4 illustrates an example of sound leakage characteristics of eachreceiver. As illustrated in FIG. 4, the amount of sound leakage in thepiezoelectric receiver is greater than in the dynamic receiver inparticular in the high frequency component of 2 kHz or more. Therefore,the equalizer 44 makes a low-range emphasis setting, to emphasize thelow frequency range more than the high frequency range of theair-conducted sound, when the volume of the air-conducted soundcollected by the microphones exceeds a predetermined threshold. As aresult, the volume in the high frequency range with a large amount ofsound leakage is suppressed, or the volume in the low frequency range isincreased, thereby satisfying receiver characteristics while alsoallowing for the reduction of an echo caused by sound leakage. Note thatthe low-range emphasis setting to emphasize the low frequency range morethan the high frequency range may include the cases of suppressing orreducing only the high frequency range without particularly processingthe low frequency range, and of emphasizing only the low frequency rangewithout particularly processing the high frequency range. Furthermore,the low-range emphasis setting to emphasize the low frequency range morethan the high frequency range may include the cases of adjusting theseranges independently from adjustment of the overall volume and ofreducing or increasing the overall volume at the same time as adjustmentof each frequency range.

For example, during the low-range emphasis setting, the equalizer 44 canvibrate the piezoelectric element 30 while reducing the frequencycomponent higher than 2 kHz and emphasizing the frequency component at 2kHz or less. In this way, in particular at high frequencies for whichsound leakage easily occurs, the amount of vibration of thepiezoelectric element 30 can be reduced, thereby suppressing or reducingsound leakage. Note that since the sound leakage characteristics varydepending on the structure of the electronic device 1, the predeterminedthreshold is of course not limited to 2 kHz. For example, thereproduction sound signal for a voice call may include frequencies from0.4 kHz to 3.4 kHz, and the predetermined threshold may be set to avalue between 0.4 kHz and 3.4 kHz. While satisfying receivercharacteristics, it is thus possible to prevent sound leakage.Alternatively, the damping ratio (or rate of increase) may be set insmall increments of 100 Hz or 500 Hz over the human hearing range.

FIG. 5 is a flowchart of low-range emphasis setting based onair-conducted sound collected by the main microphone 42. After the startof a conversation, the main microphone 42 collects air-conducted soundfrom the panel 10 (step S101). Air-conducted sound can be detected by,for example, the control unit 50 periodically sampling the output signalof the main microphone 42 and performing a frequency analysis within thetransmitted audio frequency range on the sampling output. The controlunit 50 determines whether the air-conducted sound collected by the mainmicrophone 42 exceeds a first threshold (step S102). The first thresholdis a standard for determining whether an echo is being generated in themain microphone 42 and can be set in accordance with the housingstructure, usage conditions, or the like of the electronic device 1.When the air-conducted sound collected by the main microphone 42 exceedsthe first threshold (step S102: Yes), the control unit 50 notifies theequalizer 44 accordingly. The equalizer 44 then makes a low-rangeemphasis setting to emphasize the low frequency range more than the highfrequency range (step S103). The processing in steps S101 to S103 isrepeated until either party issues a call-ending request (step S104). Itis thus possible to determine accurately the effect of an echo in themain microphone 42, which cannot cut the input signal for collectingsound by the user, and to reduce the echo.

FIG. 6 is a flowchart of low-range emphasis setting based onair-conducted sound collected by the sub-microphone 43. After the startof a conversation, the sub-microphone 43 collects air-conducted soundfrom the panel 10 (step S201). Air-conducted sound can be detected by,for example, the control unit 50 periodically sampling the output signalof the sub-microphone 43 and performing a frequency analysis within thetransmitted audio frequency range on the sampling output. The controlunit 50 determines whether the air-conducted sound collected by thesub-microphone 43 exceeds a second threshold (step S202). The secondthreshold is a standard for determining whether an echo is beinggenerated in the sub-microphone 43 and can be set in accordance with thehousing structure, usage conditions, or the like of the electronicdevice 1. When the air-conducted sound collected by the sub-microphone43 exceeds the second threshold (step S202: Yes), the control unit 50notifies the equalizer 44 accordingly. The equalizer 44 then makes alow-range emphasis setting to emphasize the low frequency range morethan the high frequency range (step S203). The processing in steps S201to S203 is repeated until either party issues a call-ending request(step S204). It is thus possible to determine accurately the soundleaking to the surrounding area and to reduce the echo.

FIG. 7 is a flowchart of low-range emphasis setting based onair-conducted sound collected by the main microphone 42 and thesub-microphone 43. After the start of a conversation, the mainmicrophone 42 collects air-conducted sound from the panel 10 (stepS301). The sub-microphone 43 also collects air-conducted sound from thepanel 10 (step S302). The control unit 50 determines whether theair-conducted sound collected by the main microphone 42 exceeds a firstthreshold or the air-conducted sound collected by the sub-microphone 43exceeds a second threshold (step S303). When the air-conducted soundcollected by the main microphone 42 exceeds the first threshold or theair-conducted sound collected by the sub-microphone 43 exceeds thesecond threshold (step S303: Yes), the control unit 50 notifies theequalizer 44 accordingly. The equalizer 44 then makes a low-rangeemphasis setting to emphasize the low frequency range more than the highfrequency range (step S304). The processing in steps S301 to S304 isrepeated until either party issues a call-ending request (step S305). Itis thus possible accurately to determine the effect of an echo in themain microphone 42 and to determine the sound leaking to the surroundingarea, and it is possible to reduce the echo.

When an echo is generated due to sound leakage in the electronic device1, it is possible to reduce the echo by the control unit 50 lowering thevolume of the air-conducted sound. FIG. 8 is a flowchart of receivervolume level setting. After the start of a conversation, the controlunit 50 sets the receiver volume level for reproducing receiver audio(step S401). Based on the receiver volume level that is set, the controlunit 50 adjusts the strength of the electric signal applied to thepiezoelectric element 30. Next, the main microphone 42 collectsair-conducted sound from the panel 10 (step S402). The sub-microphone 43also collects air-conducted sound from the panel 10 (step S403). Thecontrol unit 50 determines whether the difference between air-conductedsound collected by the sub-microphone 43 and air-conducted soundcollected by the main microphone 42 exceeds a third threshold (stepS403). For example, when sound leakage from the piezoelectric receiveris large, air-conducted sound enters both the main microphone 42 and thesub-microphone 43. Since the sub-microphone 43 is provided nearer thepiezoelectric element 30 than the main microphone 42 is, theair-conducted sound collected by the sub-microphone 43 is larger thanthe air-conducted sound collected by the main microphone 42. The thirdthreshold is a standard for determining whether an echo is beinggenerated based on the difference between air-conducted sound collectedby the sub-microphone 43 and air-conducted sound collected by the mainmicrophone 42 and can be set in accordance with the housing structure,usage conditions, or the like of the electronic device 1. When thedifference between air-conducted sound collected by the sub-microphone43 and air-conducted sound collected by the main microphone 42 exceedsthe third threshold, the control unit 50 sets a new receiver volumelevel to be the resulting value upon subtracting a predetermined offsetfrom the current receiver volume level (step S405). Since the controlunit 50 thus controls the piezoelectric element 30 to suppress or reducevibration of the panel 10, the echo caused by sound leakage can bereduced. The predetermined offset can be set in accordance with thehousing structure, usage conditions, or the like of the electronicdevice 1. The processing in steps S402 to S405 is repeated until eitherparty issues a call-ending request (step S406). When sound leakageoccurs, it is thus possible to reduce an echo.

Embodiment 1

FIGS. 9(a) and 9(b) illustrate a housing structure of the electronicdevice 1 according to Embodiment 1. FIG. 9(a) is a front view, and FIG.9(b) is a cross-sectional view along the b-b line of FIG. 9(a). Theelectronic device 1 illustrated in FIGS. 9(a) and 9(b) is a smartphonein which a touch panel that is a glass plate is disposed on the frontface (expected contact region) of the housing 60 (for example a metal orresin case) as the panel 10. The panel 10 and the input unit 40 aresupported by the housing 60, and the display unit 20 and piezoelectricelement 30 are each adhered to the panel 10 by a joining member 70. Thejoining member 70 is adhesive with thermosetting properties, ultravioletcurable properties, or other such properties; double-sided tape; or thelike. The joining member 70 may, for example, be optical elasticityresin, which is clear and colorless acrylic ultraviolet curing adhesive.The panel 10, display unit 20, and piezoelectric element 30 are eachgenerally rectangular. The display unit 20 is connected to a circuitboard 61. The sub-microphone 43 is provided at one edge (upper part) inthe longitudinal direction of the circuit board 61, and the mainmicrophone 42 is provided at the other edge (lower part) in thelongitudinal direction. In other words, the main microphone 42 isprovided in a mouth-neighboring region of the housing 60 near the mouthof the user, and the sub-microphone 43 is provided on the opposite facefrom the panel 10 of the housing 60. An opening 62 for sound collectionby the main microphone 42 is formed in the input unit 40, as indicatedby the dashed line. An opening 63 for sound collection by thesub-microphone 43 is also formed in the housing 60. The openings 62 and63 should be blocked by a member permeable by air but not liquid.Gore-Tex (registered trademark) is an example of a member permeable byair but not liquid.

The display unit 20 is disposed in approximately the center in thetransverse direction of the panel 10. The piezoelectric element 30 isdisposed at a predetermined distance from an edge of the panel 10 in thelongitudinal direction, near the edge so that the longitudinal directionof the piezoelectric element 30 is aligned with the short sides of thepanel 10. The display unit 20 and the piezoelectric element 30 aredisposed side by side, in parallel directions, on the inner face of thepanel 10.

FIG. 10 illustrates an example of vibration of the panel 10 in theelectronic device 1 according to Embodiment 1. In the electronic device1 according to Embodiment 1, the display unit 20 is attached to thepanel 10. Therefore, it is more difficult for the lower part of thepanel 10 to vibrate as compared to the upper part of the panel 10 wherethe piezoelectric element 30 is attached. As a result, at the lower partof the panel 10, sound leakage due to vibration of the lower part of thepanel 10 is reduced. The upper part of the panel 10 is bent directly bythe piezoelectric element 30, and hence compared to the upper part,vibration dampens at the lower part. The panel 10 is bent by thepiezoelectric element 30 in the direction of the long sides of thepiezoelectric element 30 such that the portion of the panel 10immediately above the piezoelectric element 30 rises the highest ascompared to adjacent portions.

In the electronic device 1 according to the present embodiment, thepanel 10 thus deforms in conjunction with deformation of thepiezoelectric element 30 attached to the back face of the panel 10, sothat air-conducted sound and vibration sound are transmitted to anobject that contacts the deforming panel 10. As a result, air-conductedsound and vibration sound can be transmitted to the user withoutprojecting the vibrating body from the outer surface of the housing 60,thereby improving usability over the electronic device disclosed inPatent Literature 1, in which a vibrating body extremely small ascompared to the housing is pressed against a human body. Thepiezoelectric element 30 also does not damage easily, since the user'sear need not be pressed against the piezoelectric element itself.Moreover, causing the housing 60 rather than the panel 10 to deformmakes it easier for the user to drop the terminal when vibration isgenerated, whereas vibrating the panel 10 makes such dropping of theterminal unlikely.

The piezoelectric element 30 is joined to the panel 10 by the joiningmember 70. The piezoelectric element 30 can thus be attached to thepanel 10 in a way that avoids restricting the degree of freedom fordeformation of the piezoelectric element 30. The joining member 70 maybe a non-heat hardening adhesive. Such adhesive has the advantage that,during hardening, thermal stress contraction does not easily occurbetween the piezoelectric element 30 and the panel 10. The joiningmember 70 may also be double-sided tape. Such tape has the advantagethat the contraction stress when using adhesive is not easily producedbetween the piezoelectric element 30 and the panel 10.

The main microphone 42 is provided in a mouth-neighboring region of thehousing 60 near the mouth of the user. It is thus possible to determineaccurately the effect of an echo on the microphone that collects speechof the user. The sub-microphone 43 is provided on the opposite face fromthe panel 10 of the housing 60. It is thus possible to determineaccurately the sound leakage at the opposite face from the user's earand to reduce the effect of sound leakage to the surrounding area.

Embodiment 2

FIGS. 11(a), 11(b), and 11(c) illustrate a housing structure of theelectronic device 1 according to Embodiment 2. FIG. 11(a) is a frontview, FIG. 11(b) is a cross-sectional view along the b-b line of FIG.11(a), and FIG. 11(c) is a cross-sectional view along the c-c line ofFIG. 11(a). The electronic device 1 illustrated in FIGS. 11(a) to 11(c)is a clamshell mobile phone in which a cover panel (an acrylic plate)protecting the display unit 20 is disposed on the front face (expectedcontact region) at the upper side of the housing 60 as the panel 10. InEmbodiment 2, a reinforcing member 80 is disposed between the panel 10and the piezoelectric element 30. The reinforcing member 80 is, forexample, a resin plate, sheet metal, or a resin plate including glassfiber. In other words, in the electronic device 1 according toEmbodiment 2, the piezoelectric element 30 and the reinforcing member 80are adhered by the joining member 70, and furthermore the reinforcingmember 80 and the panel 10 are adhered by the joining member 70.Furthermore, in Embodiment 2, the display unit 20 is not adhered to thepanel 10, but rather is supported by the housing 60. In other words, inthe electronic device 1 according to Embodiment 2, the display unit 20is separated from the panel 10 and is joined to a support 90, which is aportion of the housing 60, by the joining member 70. The support 90 isnot limited to being a portion of the housing 60 and may be configuredusing metal, resin, or the like to be a member independent from thehousing 60. The sub-microphone 43 is provided at the upper side of thehousing 60, and the main microphone 42 is provided at the lower side. Inother words, the main microphone 42 is provided in a mouth-neighboringregion of the housing 60 near the mouth of the user, and thesub-microphone 43 is provided on an opposite face from the panel 10 ofthe housing 60. An opening 62 for sound collection by the mainmicrophone 42 is formed on the front face of the housing 60 at the lowerside, facing the main microphone 42. An opening 63 for sound collectionby the sub-microphone 43 is also formed on the back face of the housing60. The openings 62 and 63 should be blocked by a member permeable byair but not liquid. Gore-Tex (registered trademark) is an example of amember permeable by air but not liquid.

FIG. 12 illustrates an example of vibration of the panel 10 in theelectronic device 1 according to Embodiment 2. In the electronic device1 according to Embodiment 2, the panel 10 is an acrylic plate with lowerrigidity than a glass plate, and the display unit 20 is not adhered tothe back face of the panel 10. Therefore, as compared to the electronicdevice 1 according to Embodiment 1 illustrated in FIG. 10, the amplitudeproduced by the piezoelectric element 30 is greater. Moreover, the panel10 vibrates not only in the region in which the piezoelectric element 30is attached, but also in a region separate from the attachment region.Therefore, in addition to air-conducted sound, the user can hearvibration sound by contacting the ear to any position on the panel 10.

In the electronic device 1 according to the present embodiment, thereinforcing member 80 and the panel 10 deform in conjunction withdeformation of the piezoelectric element 30 attached to the panel 10 viathe reinforcing member 80, so that air-conducted sound and vibrationsound are transmitted to an object that contacts the deforming panel 10.As a result, air-conducted sound and vibration sound can be transmittedto the user without the user's ear being pressed against the vibratingbody itself. Furthermore, the piezoelectric element 30 is attached tothe surface of the panel 10 that faces the inside of the housing 60.Air-conducted sound and vibration sound can thus be transmitted to theuser without projecting the vibrating body from the outer surface of thehousing 60. Moreover, the panel 10 deforms not only in the region inwhich the piezoelectric element 30 is attached, but rather throughoutthe panel 10 in order to transmit air-conducted sound and vibrationsound. Therefore, in addition to air-conducted sound, the user can hearvibration sound by contacting the ear to any position on the panel 10.

Disposing the reinforcing member 80 between the piezoelectric element 30and the panel 10 can reduce the probability of an external force beingtransmitted to and damaging the piezoelectric element 30 if, forexample, such a force is applied to the panel 10. Moreover, even if thepanel 10 is pressed firmly against a human body, vibrations of the panel10 do not dampen easily. By disposing the reinforcing member 80 betweenthe piezoelectric element 30 and the panel 10, the resonance frequencyof the panel 10 also decreases, thereby improving the acousticcharacteristics in the low frequency band. Note that instead of thereinforcing member 80, a plate-shaped anchor may be attached to thepiezoelectric element 30 by the joining member 70.

The main microphone 42 is provided in a mouth-neighboring region of thehousing 60 near the mouth of the user. It is thus possible to determineaccurately the effect of an echo on the microphone that collects speechof the user. The sub-microphone 43 is provided on the opposite face fromthe panel 10 of the housing 60. It is thus possible to determineaccurately the sound leakage at the opposite face from the user's earand to reduce the effect of sound leakage to the surrounding area.

Although the present invention has been described by way of embodimentswith reference to the accompanying drawings, it is to be noted thatvarious changes and modifications will be apparent to those skilled inthe art based on the present disclosure. Therefore, such changes andmodifications are to be understood as included within the scope of thepresent invention. For example, the functions and the like included inthe various members and steps may be reordered in any logicallyconsistent way. Furthermore, components or steps may be combined intoone or divided.

For example, as illustrated in FIG. 13, the panel 10 may be joined tothe housing 60 by the joining member 70. Making it difficult forvibration to be transmitted directly from the panel 10 to the housing 60in this way reduces the risk of the user dropping the electronic device1 as compared to when the housing itself vibrates significantly. Thejoining member 70 may be a non-heat hardening adhesive. Such adhesivehas the advantage that, during hardening, thermal stress contractiondoes not easily occur between the housing 60 and the panel 10. Thejoining member 70 may also be double-sided tape. Such tape has theadvantage that the contraction stress when using adhesive is not easilyproduced between the housing 60 and the panel 10.

For example, when the panel 10 and the display unit 20 do not overlap,the piezoelectric element 30 may be disposed at the center of the panel10. When the piezoelectric element 30 is disposed at the center of thepanel 10, vibration of the piezoelectric element 30 is transmitteduniformly across the entire panel 10, thereby improving quality ofair-conducted sound and permitting recognition of vibration sound whenthe user contacts the ear to any of various positions on the panel 10.As in the above-described embodiments, a plurality of piezoelectricelements 30 may also be provided.

The piezoelectric element 30 is attached to the panel 10 in the aboveelectronic device 1 but instead may be attached to a location other thanthe panel 10. For example, the piezoelectric element 30 may be attachedto a battery lid that is attached to the housing 60 and covers abattery. Since the battery lid is often attached to a different facethan the panel 10 in the electronic device 1 that is a mobile phone orthe like, according to this structure the user can hear sound bycontacting a part of the body (such as the ear) to a different face thanthe panel 10.

Furthermore, the panel 10 may constitute a portion or the entirety ofany of a display panel, an operation panel, a cover panel, or a lidpanel that allows for removal of a rechargeable battery. In particular,when the panel 10 is a display panel, the piezoelectric element 30 isdisposed on the outside of a display region fulfilling a displayfunction. This offers the advantage of not blocking the display. Theoperation panel includes the touch panel of Embodiment 1. The operationpanel also includes a sheet key, in which the tops of operation keys areintegrally formed in, for example, a clamshell mobile phone so as toconstitute one face of the housing alongside an operation unit.

Note that in Embodiments 1 and 2, the joining member that adheres thepanel 10 and the piezoelectric element 30, the joining member thatadheres the panel 10 and the housing 60, and the like have beendescribed as the joining member 70, using the same reference numeral.The joining members used in Embodiments 1 and 2, however, may differ asneeded in accordance with the components being joined.

For example, in the above-described embodiments, an example of theusable frequency range for audio has been described as being the rangeof 0.4 kHz to 3.4 kHz for a reproduction sound signal pertaining to avoice call, yet the usable frequency range is not limited in this way.The present invention is also applicable when using, for example, anaudio signal for which the usable frequency range is from 0.1 kHz to 7kHz. In this case, the low frequency range may be from 0.1 kHz to 5 kHzand the high frequency range from over 5 kHz to 7 kHz. These ranges forthe low frequency range and the high frequency range may of course bemodified as necessary from the perspectives of piezoelectric elementperformance, panel characteristics, power consumption, sound leakage,and the like.

REFERENCE SIGNS LIST

1: Electronic device

10: Panel

20: Display unit

30: Piezoelectric element

40: Input unit

50: Control unit

41: Transceiver

42: Main microphone (first microphone)

43: Sub-microphone (second microphone)

44: Equalizer

60: Housing

61: Circuit board

62: Opening

63: Opening

70: Joining member

80: Reinforcing member

90: Support

The invention claimed is:
 1. An electronic device comprising: apiezoelectric element; a vibrating plate configured to vibrate due tothe piezoelectric element; a first microphone configured to collectspeech of a user; a second microphone configured to collect surroundingsound; and an equalizer, the electronic device causing the vibratingplate to generate air-conducted sound and vibration sound that istransmitted by vibrating a part of a human body, and the equalizermaking a low-range emphasis setting, to emphasize a low frequency rangemore than a high frequency range of the air-conducted sound, when avolume of the air-conducted sound collected by the first microphoneexceeds a first threshold or when a volume of the air-conducted soundcollected by the second microphone exceeds a second threshold.
 2. Theelectronic device according to claim 1, wherein the vibrating plate ispositioned in an expected contact region of a housing where an ear of auser is expected to contact, and the first microphone is provided in amouth-neighboring region of the housing near a mouth of the user.
 3. Theelectronic device according to claim 1, wherein the vibrating plate ispositioned in an expected contact region of a housing where an ear of auser is expected to contact, and the second microphone is provided on anopposite face from the vibrating plate of the housing.
 4. A method forcontrolling an electronic device that includes a piezoelectric element,a vibrating plate configured to vibrate due to the piezoelectricelement, a first microphone configured to collect speech of a user, asecond microphone configured to collect surrounding sound, and anequalizer, the electronic device causing the vibrating plate to generateair-conducted sound and vibration sound that is transmitted by vibratinga part of a human body, the method comprising the step of: making alow-range emphasis setting, for the equalizer to emphasize a lowfrequency range more than a high frequency range of the air-conductedsound, when a volume of the air-conducted sound collected by the firstmicrophone exceeds a first threshold or when a volume of theair-conducted sound collected by the second microphone exceeds a secondthreshold.
 5. An electronic device comprising: a piezoelectric element;a vibrating plate configured to vibrate due to the piezoelectricelement; a main microphone; a sub-microphone; and a control unit, theelectronic device causing the vibrating plate to generate air-conductedsound and vibration sound that is transmitted by vibrating a part of ahuman body, and the control unit controlling the piezoelectric elementso as to suppress or reduce vibration of the vibrating plate when adifference between a volume of the air-conducted sound collected by thefirst microphone and a volume of the air-conducted sound collected bythe second microphone exceeds a predetermined threshold.
 6. A method forcontrolling an electronic device that includes a piezoelectric element,a vibrating plate configured to vibrate due to the piezoelectricelement, a main microphone, a sub-microphone, and a control unit, theelectronic device causing the vibrating plate to generate air-conductedsound and vibration sound that is transmitted by vibrating a part of ahuman body, the method comprising the step of: controlling, via thecontrol unit, the piezoelectric element so as to suppress or reducevibration of the vibrating plate when a difference between a volume ofthe air-conducted sound collected by the first microphone and a volumeof the air-conducted sound collected by the second microphone exceeds apredetermined threshold.